The invention pertains to an image processing method and device for reproducing original images that are stored in the form of pixels at a different scale.
Images frequently need to be reproduced on output devices, such as monitors and printers, at a different scale relative to the original image, i.e., in enlarged or reduced form. The original image information is represented by intensity values that are stored at addresses of an electronic storage medium, and the addresses of the image intensity values are assigned to certain area elements of the image that are also referred to as pixels. It is common practice to store the intensity values of the individual pixels point-by-point in a row, with the rows being stored successively, i.e., in the form of a matrix of columns and rows. In a 1:1 reproduction, each pixel of the output device reflects the intensity value of the associated pixel of the original image. In the known Nearest Neighbor Interpolation method, only the intensity values of those area elements which spatially lie closest to the pixels of the output device are respectively utilized. When reproducing a reduced image, for example, at a scale of 1:2, with this interpolation method, only every fourth pixel of the original image would be reproduced, and the originally existing image information would not be utilized in its entirety.
This also applies, in principle, to known image processing methods of higher order, e.g., the bilinear interpolation or bicubic interpolation methods, in which the intensity values of the pixels of the output device are calculated in a distance-weighted fashion relative to the spatial position of the original pixels. One common aspect of all these methods is that the stored intensity values for the pixels of the original image are processed in the form of raster points, and that the two-dimensional size of the pixels that corresponds to their physical reality is not part of the image information utilized. However, it has been recognized that an improved reproduction, by comparison to this known state of the art, can be achieved if the intensity values of the pixels are not processed in a distance-weighted, but rather in an area-weighted fashion.